str_format = "my name is {}, i'm {} years old!".format("shawn", 20)
print(str_format) # my name is shawn, i'm 20 years old!

import math

print("PI is {}".format(math.pi)) # PI is 3.141592653589793
print("PI is {:.4f}".format(math.pi)) # PI is 3.1416
print("PI is {:9.4f}".format(math.pi)) # PI is    3.1416
print("PI is {:< 9.4f}".format(math.pi)) # PI is  3.1416
